How to Prepare Grain Spawn Jars with Wild Bird Seed (WBS)

How to Prepare Grain Spawn Jars with Wild Bird Seed (WBS)

Simple, Cheap, and Perfect for Almost Any Mushroom Species

When I first started growing mushrooms, I wasn’t looking to spend a lot or overcomplicate things. I was just a curious guy with a love for functional mushrooms and a desire to create something real from scratch. That’s when I discovered wild bird seed (WBS) — one of the easiest, cheapest, and most versatile substrates for making grain spawn at home. Years later, even after running a legit lab and tincture business, I still come back to WBS for its reliability and simplicity.

This guide is for beginners and hobbyists who want to inoculate grain jars with liquid culture, agar wedges, or even tissue cultures. Whether you're growing Lion’s Mane, Reishi, or Cordyceps (with a few tweaks), this process will give you clean, nutrient-rich grain spawn ready to colonize.

Why Use Wild Bird Seed?

✅ Cheap and easy to find (Walmart, pet stores, hardware stores)
✅ Nutrient-rich: millet, milo, sunflower seeds (optional to remove)
✅ Works for most species: Lion’s Mane, Reishi, Oysters, and more
✅ Flexible format: Works well in jars or grow bags

What You'll Need

  • Wild Bird Seed (no cracked corn is best)

  • Quart-size Mason jars with metal lids & rings

  • Polyfill, micropore tape, or synthetic filter disks

  • Pressure cooker (preferably 15 PSI)

  • Strainer or colander

  • Large pot for soaking and boiling

  • Optional: gypsum (helps with clumping)

Step-by-Step Instructions

🔹 Step 1: Rinse & Soak Your Seed

Dump your WBS into a strainer and rinse thoroughly to wash off dirt and dust. Soak in clean water (about 2x the volume of seed) for 12–24 hours. This hydrates the grains and starts germination.

Tip: Add a tablespoon of gypsum to help prevent clumping.

🔹 Step 2: Simmer for Hydration

Bring your WBS to a gentle boil for 10–15 minutes. The grains should be plump but not bursting. You should be able to squish them between your fingers.

🔹 Step 3: Strain and Dry

Strain the grains and let them steam-dry for 30–60 minutes. They should feel dry on the outside but fully hydrated inside.

🔹 Step 4: Fill Your Jars

Fill jars about 2/3 full. Drill a 1/4” hole in the lid and use polyfill, micropore tape, or a synthetic filter disk for gas exchange.

🔹 Step 5: Pressure Cook

Sterilize jars at 15 PSI for 90 minutes. Let them cool fully before inoculating.

Pro Tip: Let them cool overnight to avoid temperature shock.

🔹 Step 6: Inoculate

Once jars are fully cool, you can:

  • Inject liquid culture using sterile technique

  • Add agar wedges in a glove box or flow hood

  • Use grain-to-grain transfer from a clean jar

🔹 Step 7: Shake & Wait

Once you see 20–30% colonization, shake gently to redistribute the mycelium. Let jars fully colonize in a clean, ambient area.

Final Thoughts

Making your own grain spawn is empowering, cost-effective, and rewarding. Wild bird seed is how I started, and it’s still one of my go-to methods. If you’re getting into mushroom cultivation or want to improve your setup, give this method a shot.

Want more guides like this?
Check out the full How-To series at MushroomSupplementGuide.com

— Bobby Bernard
Founder, South Middle Mushrooms

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